JP2002287516A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method by which wasteful consumption of toner and carrier is restrained and also an occurrence of abnormal discharge with an image carrier is avoided. SOLUTION: A sweep roller SR is made to abut on an image carrier 1 and also specified bias is applied to the roller SR before a front preliminary area β2 which is coated with developer in a non-image area on a front side on the image carrier 1 reaches an opposed part to the roller SR, and the roller SR is separated from the image carrier 1 and also the application of the bias is stopped when and after a rear area γ1 which is not coated with the developer in the non-image area on a rear side reaches the opposed part to the roller SR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a developing roller for developing on an image carrier and a sweep roller for removing unnecessary toner on the image carrier.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a copying machine,
Around an image carrier such as a photoconductor, an exposure device, a developing device,
2. Description of the Related Art A device provided with a transfer device, a fixing device, a charge removing device, a cleaning device, a charging device, and the like is widely known.

For example, in this copying machine, a charging device initially applies a potential of about 600 V to a photoconductor, for example, a-Si (amorphous silicon photoconductor) or OPC (organic photoconductor). Thereafter, an image area on the photoconductor is exposed by an exposure device such as an LED or a laser scanning optical system to form an electrostatic latent image, and toner is applied to the electrostatic latent image by a developing device constituting a developing device. This is electrostatically attracted to visualize this.

On the other hand, the toner visualized by the developing device and adsorbed and carried on the photoreceptor is transferred and transferred to the transfer paper by electrostatic force by a transfer roller as a transfer device. Then, the toner on the transfer paper is thermally fused by the fixing device to complete the copying operation, and unnecessary toner remaining on the photoreceptor is removed by the cleaning device. The charge is removed up to the initial potential by a certain charge removing roller, and is prepared for the next copying operation.

[0005]

As described above, the toner adhered on the photoreceptor by the developing device is consumed by being adhered to the transfer paper by the transfer device as described above. The toner may adhere to unnecessary portions.

However, such a developing device usually has no means for collecting the toner, and the toner there is also transferred to a transfer sheet at the same time and consumed together, which is uneconomical. On the other hand, if the carrier adheres to the photoreceptor in the vicinity of the developing device and is carried as it is to a transfer area where the transfer device is located, the carrier may be transferred to the transfer paper and consumed. Has become.

In view of the above circumstances, the present invention provides an image forming method capable of suppressing wasteful consumption of toner and carrier and preventing occurrence of abnormal discharge with an image carrier. It is intended to do so.

[0008]

According to a first aspect of the present invention, there is provided an image forming method for developing an image on an image area of an image carrier on which an electrostatic latent image is formed. Image formation using a developing roller that can be separated from and separated from the image carrier, and a sweep roller that can be separated from the image carrier that collects and removes carrier liquid after development and unnecessary toner adsorbed in the non-image area A method, wherein an image area or a non-image area reaches an opposing portion of a sweep roller on the image carrier or an operation in which an image area or a non-image area arrives or passes therethrough, with respect to a sweep roller and / or a developing roller. It is characterized in that the operation of contacting and separating from the image carrier and the operation of applying a bias voltage are controlled.

According to a second aspect of the present invention, in the image forming method according to the first aspect, before the area on the image carrier on which the developer is applied reaches the portion facing the sweep roller. Then, the sweep roller is brought into contact with the image carrier and a predetermined bias is applied to the sweep roller, and after the area where the developer is not applied reaches the portion facing the sweep roller, the sweep roller is moved to the image position. It is characterized in that it is separated from the carrier and the bias is cut off.

According to the second aspect of the present invention, since the sweep roller is in contact with the image carrier and a bias is applied before facing the developer layer, most of the toner on the image is removed. And the carrier liquid can be recovered. Thereby, it is possible to prevent the carrier liquid from being transferred to the next step (such as an intermediate transfer member or transfer paper). If the carrier liquid is transferred to the transfer paper, it cannot be recovered in the machine, and if the carrier liquid is transferred to the intermediate transfer body, the carrier liquid of the intermediate transfer body will be removed in addition to the carrier liquid remaining on the image carrier. Is also collected, which makes the apparatus and process complicated.

In the image forming method according to a third aspect, in the image forming method according to the second aspect, the sweep roller is brought into contact with the image carrier and the bias is turned off before the bias is applied. Thereafter, the sweep roller is separated from the image carrier.

When the sweep roller contacts the image carrier on which the developer layer is not applied while a bias is applied to the sweep roller, the discharge limit is reached when the distance between the sweep roller and the image carrier gradually approaches, The latent image may be discharged. Therefore, in the invention according to claim 3, by applying a bias after the sweep roller comes into contact with the image carrier, such a problem is prevented, and the carrier in the image portion is hardly removed while removing the toner. Can be collected and removed.

According to the third aspect of the present invention, after the rear end of the developer layer on the image carrier has passed, the bias applied to the sweep roller is turned off, and then the sweep roller is moved to the image carrier. By separating from the carrier, more carriers can be removed without causing abnormal discharge or the like. This is because if the roller is separated from the photoconductor in a state where an electric field is applied, discharge may occur.

According to a fourth aspect of the present invention, in the image forming method of the second aspect, the developing roller comes into contact with the image carrier only when the developer is applied on the developing roller. Before a predetermined time elapses from the time when the developing roller contacts the image carrier, the sweep roller starts to contact the image carrier.

According to the fifth aspect of the present invention, the developing roller and the sweep roller can be brought into contact with and separated from the image carrier, and when the developing roller comes into contact with the photosensitive member, the developer is placed on the developing roller. When the sweep roller is in contact with the image carrier, the timing at which the sweep roller comes into contact with the image carrier is set X seconds after the developing roller comes into contact with the image carrier. It can be defined by the time between the timing when the developing roller contacts the image carrier. Thereby, when setting the sequence, the sequence can be set efficiently.

According to a fifth aspect of the present invention, in the image forming method according to the first aspect, before the image area reaches the portion facing the sweep roller, the sweep roller is moved to the image carrier. A predetermined bias is applied to the sweep roller while being brought into contact with the sweep roller.After the rear end of the image area passes through a portion facing the sweep roller, the sweep roller is separated from the image carrier, and the bias is applied. It is characterized by cutting. According to the fifth aspect of the invention, before the image area corresponding to the transfer paper arrives on the image carrier, the sweep roller contacts the image carrier and the bias is applied,
The amount of transfer of the carrier liquid to the transfer paper can be reduced. Also, almost no toner on the image is removed,
More carriers can be collected.

According to a sixth aspect of the present invention, in the image forming method of the fifth aspect, when the sweep roller is brought into contact with the image carrier and the bias is applied, the sweep roller is placed on the image carrier. When the developer is applied, the bias is applied before the sweep roller is brought into contact with the image carrier. According to the invention described in claim 6, by applying a bias to the sweep roller before the sweep roller contacts the image carrier,
At the same time as the sweep roller comes into contact with the image carrier, more carrier can be removed with little toner in the image area. This is because if the sweep roller contacts the image carrier before the bias is applied, the toner in the image area may adhere to the sweep roller.

Further, according to the present invention, the developing roller and the sweep roller can be brought into contact with and separated from the image carrier, and when the developing roller comes into contact with the image carrier, it is placed on the developing roller. When the developer is applied, the sweep roller comes into contact with the image carrier only X seconds after the development roller comes into contact with the image carrier, so that the sweep roller comes into contact with the image carrier. The timing can be defined by the time from the timing when the developing roller contacts the image carrier. Thereby, when setting the sequence, the sequence can be set efficiently.

According to a seventh aspect of the present invention, there is provided the image forming method according to the fifth aspect, wherein a non-image area is formed after passing the image area through a portion of the image carrier opposite the sweep roller. While passing through the preliminary area after the developer in the area is applied, the sweep roller is separated from the image carrier,
After separating the sweep roller from the image carrier,
The bias applied to the sweep roller is turned off. According to the invention described in claim 7, after the sweep roller is separated from the image carrier after the portion corresponding to the transfer paper on the image carrier and in the region where the developer is applied,
By turning off the bias applied to the sweep roller, more carriers can be removed with little removal of toner in the image area. This is because if the sweep roller is in contact with the image carrier even after the bias is turned off, the toner in the image area may adhere to the sweep roller.

Further, the image forming method according to the present invention is characterized in that:
2. The image forming method according to claim 1, wherein after a preparatory area on which a developer in a non-image area is applied reaches a portion on the image carrier facing a sweep roller, and wherein Before the front end reaches, while applying a predetermined bias to the sweep roller, after the rear end of the image area passes through the facing portion with the sweep roller,
In addition, the bias is turned off before the rear area where the developer is not applied in the rear non-image area reaches.

According to the present invention, by applying a bias only to a portion where the developer layer is present on the image carrier, the latent image is prevented from being discharged, and the toner on the image is prevented from being discharged. The carrier liquid can be recovered with almost no removal. As a result, it is possible to prevent the carrier liquid from being transferred to the next step (such as an intermediate transfer member or transfer paper).

The image forming method according to claim 9 is
2. The image forming method according to claim 1, wherein the sweep roller is brought into contact with the image carrier before the front preliminary area in the non-image area where the developer is applied reaches the portion facing the sweep roller. 3. , At a portion facing the sweep roller,
After the preliminary area reaches after the developer in the non-image area is applied, and before the image area reaches,
A predetermined bias is applied between the sweep roller and the image carrier to the sweep roller.

According to the ninth aspect of the present invention, the sweep roller is brought into contact with the developer layer on the image carrier immediately before the portion having the developer layer, and the sweep is applied by applying a bias at the portion where the developer layer exists. It is possible to prevent permanent deformation of the roller and abnormal discharge caused by the sweep roller.

According to a tenth aspect of the present invention, there is provided the image forming method according to the first aspect, wherein the developer in the non-image area is applied to a portion facing the sweep roller. After the area is reached, the sweep roller to which a predetermined bias is applied is brought into contact with the image carrier.

According to the tenth aspect of the present invention, the sweep roller to which the bias is applied is brought into contact with the image carrier at a portion where the developer layer on the image carrier is present. At the same time, the carrier liquid on the image carrier can be collected and removed with little removal of the toner on the image. As a result, it is possible to prevent the carrier liquid from being transferred to the next step (such as an intermediate transfer member or transfer paper).

An image forming method according to an eleventh aspect of the present invention is the image forming method according to the first aspect, wherein the developer in the non-image area is applied to a portion facing the sweep roller. After the area reaches, the sweep roller is brought into contact with the image carrier, and thereafter, a predetermined bias is applied to the sweep roller, and after the rear end of the image area reaches the portion facing the sweep roller. In addition, the bias is turned off and the sweep roller is separated from the image carrier before the rear area of the non-image area where the developer is not applied arrives.

According to the eleventh aspect of the present invention, a bias is applied to the sweep roller after the sweep roller is brought into contact with the image carrier at a portion where the developer layer on the image carrier is present. When the sweep roller to which the bias is applied contacts the image carrier, the carrier liquid on the image carrier can be collected and removed without causing abnormal discharge or the like. As a result, the carrier liquid can be recovered without transferring the carrier liquid to the next step (intermediate transfer body, transfer paper, etc.) as much as possible, and with little removal of the toner on the image. Further, in a portion where the developer layer on the image carrier is present, the bias applied to the sweep roller is turned off, and the sweep roller is separated from the image carrier to remove the carrier liquid on the image carrier. Abnormal discharge and permanent deformation of the sweep roller can be prevented.

According to a twelfth aspect of the present invention, in the image forming method of the first aspect, when the developer is applied on the developing roller, the developing roller is brought into contact with the image carrier. And X seconds from the time when the developing roller comes into contact with the image carrier (where X = L / v,
L: the distance between the developing roller and the sweep roller on the image carrier, v: the linear velocity of the image carrier, the bias is applied to the sweep roller after elapse, and the developer is applied on the developing roller. In this case, the developing roller is separated from the image carrier while the developing roller is separated from the image carrier, and the bias is turned off before the lapse of the X seconds from when the developing roller is separated from the image carrier.

According to the twelfth aspect of the present invention, the timing at which the sweep roller contacts the image carrier can be defined by the time between the timing at which the developing roller contacts the image carrier. Can be set efficiently. Further, the timing of separating the sweep roller from the image carrier can be defined by the time from the timing of separating the developing roller from the image carrier, and can be set efficiently when setting a sequence.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Prior to describing the image forming method of the present invention, an image forming apparatus to which the method is applied will be described.

FIG. 1 shows a copying machine provided with a developing device to which the image forming method according to the first embodiment of the present invention is applied. This copying machine includes a photosensitive member 1 serving as an image bearing member. Around the periphery, an exposure device 2, a developing device 3, a transfer device 4, a fixing device (not shown), a charge removing device 5, a cleaning device 6, a charging device 7, and the like are provided. Use to make a copy. In this embodiment,
Although a copying machine is used as an image forming apparatus to which the image forming method is applied, the present invention is not limited to this.

The photosensitive member 1 has a drum shape, and a-Si (amorphous silicon) is used on the outer peripheral surface on which an electrostatic latent image is formed. This photoconductor 1
As shown in FIG. 2, when copying a document made of, for example, one cut sheet, the non-image area β and the image area α on the outer peripheral surface are arranged in order from the upstream side in the transport direction. ,
The (rear) non-image area γ is arranged adjacently.

The (non-image area) β (front side) includes a front area β 1 on which a developer (in this case, a liquid carrier (carrier liquid)) is not applied, and a front idling area ( Hereinafter, it is referred to as a preliminary spare area.
In particular, in the front preliminary area β2, the developing roller starts to contact the photoconductor 1, and the developer, particularly, the carrier liquid is applied.

The (non-image area) γ (on the rear side) has the same structure as the non-image area β (on the front side), and the rear idling area (hereinafter, referred to as a developer), particularly, a carrier liquid is applied.
Γ2) and a rear area γ1 to which the carrier liquid subsequent to the subsequent preliminary area γ2 is not applied.

On the other hand, the image area α has a size substantially corresponding to the size of the transfer paper. An electrostatic latent image is formed, and toner is electrostatically adsorbed according to the latent image. An image portion α1 to which toner is adsorbed and a background portion α2 other than the image portion α1. Of these, the background part α2
Corresponds to an area where the electrostatic latent image is not formed and the toner is not attached in the image area α.

In this embodiment, a drum-shaped image carrier is used, but a belt-shaped image carrier may be used instead.

The developing device 3 includes, in particular, a DSR developing device (Dev
elopment Apparatus using Development and Sweep Rol
lers). The DSR developing device is of a liquid developing type using a liquid as a developer, and generally includes a developing roller (hereinafter, referred to as DR) 31, a supply unit 32, and a feedback unit 33. I have. Further, the developing device 3 includes a sweeper (hereinafter referred to as SR) near the developing roller 31 and downstream of the photoconductor 1 in the rotation direction.
(Referred to as 34).

Each of the DR 31 and the SR 34 has a moving mechanism and a control unit (not shown) for controlling the operation of the moving mechanism. The DR 31 and the SR 34 are connected to the photosensitive member 1 at appropriate timing described later. Contact or separation.

Further, the DR 31 and the SR 34 include:
At an appropriate timing, respectively, DR31 and SR34
And a rotation mechanism (not shown) for independently and rotationally driving the motors, and their operations are controlled by the above-described control unit.

In addition to controlling the moving mechanism and the driving mechanism, the control section applies and controls a required bias voltage, which will be described later, to the DR 31 and the SR 34 at a predetermined timing.

Incidentally, these DR31 and SR34 include:
In order to adjust the nip widths Wd (see FIG. 3) and Ws (see FIG. 4) formed by pressure contact with the photoconductor 1, it has a structure including a layer of an elastic material such as rubber. The reason why the nip widths Wd and Ws are provided is that a certain development time is required for the toner to move and adhere to the photoconductor by the developing electric field in the developing area.

Here, the developer has a low viscosity (about 1 cSt) using Isopar (trade name, manufactured by Exxon) as a carrier.
Although a liquid developer having a low concentration (about 1%) may be used, a liquid developer having a high viscosity and a high concentration is particularly used. Various properties required for the developer used include a viscosity of 50 cSt or more and 5
000 cSt or less, the concentration is between 5% and 40%.
As the carrier liquid, a liquid having high insulation properties such as silicone oil, normal paraffin, Isopar M, vegetable oil, and mineral oil is used. Volatility and non-volatility are selected according to the purpose. The particle size of the toner can be selected from submicron to about 6 μm according to the purpose.

A thin layer of developer (hereinafter referred to as a developer layer) (for example, 5 to 10 μm) is applied to the DR 31 by applying means such as a gravure roller or anilox roller 35.
m) is formed, and the DR on which the developer layer is formed
The surface on 31 moves at substantially the same peripheral speed as photoconductor 1. Note that this developer layer forms the above-described nip Wd sandwiched between the photoconductor 1 and the DR 31.

Further, a developing bias voltage (400 V) lower than the surface potential of the photoconductor 1 is applied to the DR 31, and the development is performed between the DR 31 and the image surface on the photoconductor 1 that has been exposed to 50 V or less. Generates an electric field. The toner constituting the developer on the DR 31 moves to the photoreceptor 1 by the Coulomb force generated by the electric field, and becomes visible.

For the background portion α2 on the photoreceptor 1, the DR
The toner is attracted and moved to the surface of the DR 31 by an electric field formed by the bias potential of the photoconductor 31 and the photoconductor potential of the photoconductor 1, so that the toner does not adhere to the background portion α2.

On the other hand, the SR 34 is for removing excess carrier liquid, toner adhered to the non-image area γ, and the like from the developer layer on the photoreceptor 1 after development. If a part of the toner in the portion α2 does not move to the surface of the developing roller 31 and remains on the photosensitive member 1 side, it causes fogging, and is removed. In addition, the SR 34 is disposed on the downstream side in the rotation direction of the DR 31 in such a state that the developed toner layer is sandwiched therebetween.
It is installed in a state where it can be pressed. A bias voltage close to the surface potential of the toner layer on the photoreceptor 1, for example, 250 V, is applied to the SR in order to prevent the toner from returning from the toner layer to the SR after the development. Further, the SR 34 has a function of sucking and moving the floating toner by an electric field generated by a difference between this potential and a potential of a background portion α2 of the photoconductor 1 described later.

At this stage, the developer layer of the background portion α2 is about half the thickness of the nip portion of the developing roller 31, and the toner density is reduced to about 20% of the density before development. By installing the SR 34, the fog toner can be easily removed. Thereby, it is possible to completely remove the fog of the background portion α2.

Further, by installing the SR 34, the fog can be efficiently removed.
It is not a problem even if some fogging occurs at 31, so that the fog removal electric field, that is, the potential difference between the developing bias applied to the DR 31 and the charging potential of the photoconductor 1 can be suppressed low. This makes it possible to lower the charging potential of the photoconductor 1. As a result, the durability of the photoconductor 1 and the load on the charger can be reduced, and effects such as a reduction in exposure power can be obtained.

Further, by providing the SR 34, the developing portion and the fog removing portion can be separated. For this reason, in the conventional configuration using one developing roller, development and fog removal are performed simultaneously in the state of the high-concentration developer, so that a relatively long development time, for example, about 40 msec, is required. That is, by installing this SR34, each DR31,
Since the area where the nip width is formed due to the contact of the SR 34 with the photoreceptor 1 can be reduced, both the DR 31 and the S
The weight of R34 can be suppressed, and the durability is improved accordingly.

Next, the image forming method of the present invention, in particular, the developing method will be specifically described below. This image forming method will be described based on an image forming apparatus provided with the developing device described above. <First Embodiment> In the developing device of the first embodiment, as shown in FIG. 5, development is performed by a liquid development method having DR31 and SR34. In FIG. 5 and subsequent figures, the length of the image area α is set to be typically shorter for convenience of explanation, unlike the actual case.

In this developing method, the photosensitive member 1 is controlled by a control unit (not shown) at the timings shown in FIGS.
Is controlled so that the SR 34 moves toward and away from the main body and rotates. A required bias voltage is applied to this SR 34 at the timing shown in FIG. (1) That is, first, the SR 34
When the front preliminary area β2 on the photoconductor 1 reaches the opposing portion (hereinafter, referred to as an SR opposing portion) of the photoconductor 1 (time t01 ′), the preparatory area β2 contacts the photoconductor 1 (See FIG. 5C). (2) Next, in the SR 34, the photoconductor 1
Is reached (time t01), the image area α1 in the image area α on the photoconductor 1
A bias voltage V1 is applied so as to form an electric field that does not peel off the toner particles attached to the substrate (FIG. 5).
(B)). (3) Thereafter, when the rear end of the non-image area γ on the photoconductor 1 on the photoreceptor 1 and the rear end of the preparatory area γ2, that is, the rear area γ1 arrives (time t23), the SR The bias voltage V1 in which the electric field is formed is cut off (see FIG. 5B). (4) Next, after the rear area γ1 on the photoconductor 1 reaches the SR opposing portion (time t23), (time t23 ′)
The SR is separated from the photoconductor 1 (see FIG. 5C).

Therefore, according to the first embodiment, before the image portion α1 on which the developer on the photoreceptor 1 is adsorbed reaches the SR opposing portion, the SR 34 is set to the front preliminary area β2 of the photoreceptor 1
, And then the required bias V1 is applied.

That is, as described above, this bias V1 is caused by the toner particles adhering to the background portion α2 and the surplus toner particles floating between the background portion α2 and the SR 34 in the image setting area. Is a bias voltage that generates an electric field in a direction of drawing to the SR 34 side, and an electric field that does not peel off the toner particles attached to the image portion α1 (the region other than the background portion α2) in the image region α.
There is almost no risk of removing the toner on the image portion α1.

On the other hand, the carrier liquid SR34
, The carrier liquid on the photoreceptor 1 is transferred to the SR
34 and can be collected. This allows
The trouble of transferring the carrier liquid to the next process (intermediate transfer member, transfer paper, etc.) is reduced. When the carrier liquid is transferred to the transfer paper, the carrier liquid cannot be collected in the copying machine. When the carrier liquid is transferred to the intermediate transfer body, the carrier liquid of the intermediate transfer body besides the carrier liquid remaining on the photoconductor 1 is transferred. The liquid also needs to be collected, which complicates the apparatus and process. In this embodiment, such inconvenience can be avoided.

Further, for example, when a bias is applied to the SR 34 and the SR 34 is brought into contact with the front region β1 of the photoreceptor 1 on which the developer layer is not applied, the distance between the SR 34 and the photoreceptor 1 gradually decreases. In some cases, the discharge limit is reached on the way, and eventually the electrostatic latent image is discharged. Therefore, in this embodiment, the SR 34 is
Such a problem can be avoided by applying a bias after abutment. Further, only the carrier can be removed with almost no removal of the toner in the image portion α1.

Further, when the SR 34 is separated from the photoreceptor 1 in a state where an electric field is applied, discharge may occur. In this embodiment, after the rear end a 'of the image area α on the photoreceptor 1 passes. , SR34 are turned off, and thereafter SR34 is separated from photoconductor 1. Therefore, more carriers can be removed without causing abnormal discharge or the like.

In this embodiment, as shown in FIG. 6, as described above, DR31 and SR34 are
In particular, the DR 31 is brought into contact with the photoconductor 1 only when the developer is applied on the DR 31.

On the other hand, the SR 34 is preferably brought into contact with the photosensitive member 1 before X seconds (time, t0a + X) have elapsed from the time when the DR 31 has contacted the photosensitive member 1 (time t0a).

X = L / v L: distance (mm) between the DR-facing portion and the SR-facing portion on the periphery of the photoconductor v: peripheral speed of the photoconductor (mm / s) The timing of contact with the photoconductor 1 can be defined by the time relationship with the timing of contact of the DR 31 with the photoconductor 1, and can be set efficiently when setting and controlling the sequence. <Second Embodiment> Next, a developing method according to a second embodiment will be described with reference to FIG. In this embodiment, similarly to the first embodiment, each of the DR 31 and the SR 34 includes a moving mechanism and a rotation mechanism controlled by a control unit, and uses a liquid developer as a developer. .

According to this developing method, the control unit
At the timing shown in FIG.
R34 performs a contact / separation operation, and a required bias voltage is applied by the control unit at the timing shown in FIG. (1) That is, before the leading end a of the image area α on the photoconductor 1 reaches the SR opposing portion (time t1) (for example, at time t1).
01), the SR 34 is brought into contact with the photoconductor 1. In addition, a bias voltage V1 is applied to the SR 34 in synchronism with the time t01 to form an electric field between the photoreceptor 1 and the SR 34 so as not to peel off the toner particles attached to the image portion α1. . (2) Further, when the rear end a ′ of the image area α reaches the SR-facing portion (time t2) (for example, at time t23), the moving mechanism is separated from the photoconductor 1 at the SR34. Control. The application of the bias voltage to the SR 34 is stopped in synchronization with the time t23.

Therefore, in the second embodiment, before the time t1 when the image area α reaches the SR opposing portion, the SR 34
Is in contact with the photoreceptor 1 and a required bias V1 is applied, so that a larger amount of the carrier liquid can be recovered without removing the toner in the image area α1. This is because if the SR 34 contacts the photoconductor 1 before the bias is applied,
This is because the toner of the image portion α1 may adhere to the SR 34 in some cases.

In the second embodiment, as shown in FIG. 8, when the SR 34 contacts the photosensitive member 1 and the bias V1 is applied to the SR 34 (at time t).
01 ′), when the developer is already applied on the photoconductor 1, the bias V1 is applied to the SR before the SR is brought into contact with the photoconductor.

When the SR contacts the photosensitive member 1 (t01)
By applying a bias to the SR before (′), the SR 34 comes into contact with the photoconductor 1 without substantially removing the toner adsorbed on the image area α (a to a ′) on the photoconductor 1. At the same time, more carrier liquid can be removed. This is because, when the SR 34 contacts the photoconductor 1 before the bias is applied, the image area α (a to a ′)
This is because there is a case that the toner adheres.

In the second embodiment, for example, in FIG. 9, the SR 34 is separated from the photoreceptor 1 while the rear preliminary area γ2 passes after the image area α on the photoreceptor 1. In this case, the bias applied to the SR 34 is cut off at a time when the SR 34 is separated from the photoconductor 1, for example, at a time t23 'after the time t23, for example, at a time t23'.

As a result, a larger amount of the carrier liquid can be removed without almost removing the toner in the image area α1 in the image area α. This is because the SR3
4 is in contact with the photoreceptor 1, the image portion α
This is because one toner may adhere. <Third Embodiment> Next, a developing method according to a third embodiment of the present invention will be described with reference to FIG. In this embodiment, similarly to the first embodiment, the developing device described above is used, and DR31 and SR31 are used.
Each of the units 34 includes a moving mechanism and a rotating mechanism controlled by the control unit. Note that a liquid developer is used as the developer.

In this developing method, the control unit controls
The required bias V1 is applied at the timing shown in FIG. (1) That is, for example, when the front preliminary portion β2 of the non-image region β on the upstream side of the image region α1 on the photoconductor 1 reaches the SR facing portion (t01) and after, and the SR facing portion Before the image area α reaches (t1), the bias V1 is applied to SR. This bias V1 is a potential that forms an electric field between the SR 34 and the photoconductor 1 such that toner particles adhered to the image portion α1 on the photoconductor 1 are not peeled off, similarly to the above-described embodiment. (2) Next, the image area α2 on the photoconductor 1
The bias is turned off after the rear end of the non-image area γ and before the rear end of the rear preliminary area γ2 of the non-image area γ, that is, before the rear area γ1 arrives (for example, at time t2 ′).

For example, when a biased roller is brought close to the charged photoconductor 1 or a bias is applied to a roller in contact with the charged photoconductor 1, the latent image may be discharged. For example, this can be prevented by applying the bias V1 only to the portion where the developer layer exists on the photoconductor 1.

In addition, the carrier liquid can be recovered without almost removing the toner on the image, and transfer of the carrier liquid to the next step (intermediate transfer member, transfer paper, etc.) can be avoided as much as possible. <Fourth Embodiment> Next, a developing method according to a fourth embodiment will be described with reference to FIG. Note that, also in this embodiment, the above-described developing device is used, and similarly to the first embodiment, the DR 31 and the SR 34 each include a moving mechanism and a rotating mechanism controlled by a control unit. Here, a liquid developer is used as the developer.

In this developing method, the control unit controls
The SR comes into contact with the photoconductor at the timing shown in (B), and a required bias voltage is applied at the timing shown in FIG. (1) That is, the front preliminary area β on the photoconductor 1
2 before time t01, for example, time t01 '
Then, the SR 34 is brought into contact with the photoconductor 1. (2) Next, in the SR facing portion, the front preliminary area β on the photoconductor 1
2 and after time t01 when the image area α on the photoconductor arrives at the SR opposing portion,
For example, at time t1 ', a bias is applied to SR34 so as to form an electric field between SR34 and photoconductor 1 that does not peel off the toner adhered to image portion α1 on photoconductor 1.

Therefore, the SR 34 is brought into contact immediately before the portion where the developer layer is present on the photosensitive member 1 and a bias is applied at the portion where the developer layer is present, whereby permanent deformation of the SR 34 and SR 3
4 can be prevented, and the toner on the image can be recovered with almost no removal. As a result, transfer of the carrier liquid to the next step (intermediate transfer body, transfer paper, or the like) can be avoided as much as possible. <Fifth Embodiment> Next, a developing method according to a fifth embodiment will be described with reference to FIG. 12 using the above-described developing device.

In the SR facing portion, the front preliminary area β on the photosensitive member 1
2 has arrived (time t01) and thereafter, the SR having applied the same bias V1 as the above-described voltage value between itself and the photosensitive member 1 has been applied.
34 contacts the photoconductor 1 (see FIG. 12B).

Therefore, according to this embodiment, the photosensitive member 1
In the portion where the upper developer layer exists, the biased S
By bringing R34 into contact with photoconductor 1, the carrier liquid on photoconductor 1 can be removed at the same time as SR34 comes into contact. Moreover, almost all of the carrier liquid can be recovered without removing the toner on the image portion α1. Thus, similarly, the transfer of the carrier liquid to the next step (such as an intermediate transfer body or transfer paper) can be avoided. <Sixth Embodiment> Next, a developing method according to a sixth embodiment will be described with reference to FIG. 13 using the developing device described above. (1) After the preparatory area β2 on the photoconductor 1 reaches the SR facing portion (time t01), the SR34 is changed to the photoconductor 1
Then, the same bias V1 as that described above is applied to the SR 34 between the photoconductor 1 and the photoreceptor 1 (see FIG. 3C). (2) Further, after the rear end a 'of the image area α on the photoconductor 1 reaches the SR34 opposing portion (time t2), and after the non-image area γ on the photoconductor 1, The bias V1 is turned off and the SR 34 is separated from the photoreceptor 1 until the passage, that is, before the rear area γ1 arrives (time t23) (see FIGS. 3B and 3C).

Therefore, according to this embodiment, the photosensitive member 1
In the area where the upper developer layer (insulating carrier liquid) is
By applying a bias to SR34 after contacting R34 with photoreceptor 1, when the biased SR34 contacts photoreceptor 1, the insulating carrier liquid
Abnormal discharge can be prevented. Thereby, the carrier liquid on the photoconductor 1 can be reliably collected.

Further, also in this embodiment, since the bias V1 applied to the SR 34 is suppressed to a required voltage or less, the toner on the image portion α1 in the image area α is not removed, and only the carrier liquid is used. Can be collected. Thereby, the transfer of the carrier liquid to the next step (intermediate transfer member, transfer paper, or the like) can be avoided.

Further, according to this embodiment, the photosensitive member 1
By turning off the bias applied to the SR 34 at a portion where the upper developer layer is present and separating the carrier liquid from the photoreceptor 1, when the carrier liquid on the photoreceptor 1 is collected and removed from the photoreceptor 1, the SR 34
Abnormal discharge and permanent deformation can be prevented. <Seventh Embodiment> Next, a developing method according to a seventh embodiment will be described with reference to FIG. 13 using the developing device described above.

In this embodiment, the DR 31 is used when the developer is applied thereon (time, t0b to tend).
Contact only with the photoconductor 1. On the other hand, the bias is applied to the SR 31 after X seconds from the time when the DR 31 contacts the photoconductor 1 (time t0b), that is, at time t0b +
It is later than X (see FIG. 3C). However, the time of X seconds is the same as X described above.

Similarly, the DR 31 is separated from the photoreceptor 1 by the time the developer is applied on the DR 31 (time tend), as shown in FIG. on the other hand,
The above bias applied to SR34 is cut off by the DR31
From the photosensitive member (time tend), the same X
It is before the time when the second has elapsed (see FIG. 3C).

Therefore, according to this embodiment, the SR 34
Can be defined by the time between the contact of the DR 31 with the photoreceptor 1 and the time when the DR 31 is in contact with the photoreceptor 1, so that the sequence can be set efficiently.

Further, the timing at which the SR 34 is separated from the photoconductor 1 can also be defined by the time at which the DR 31 is separated from the photoconductor 1, and the same effect can be obtained.

In these embodiments, the SR34
Is controlled so as to perform a rotating operation while in contact with the photoconductor 1. That is, this SR 34 is
Is controlled so as to start rotating before contact with the photosensitive member 1, and is controlled so as to stop rotating after separating from the photosensitive member 1.

The rotation speed of the SR 34 at this time is
The angular velocity is such that the surface velocity of the SR 34 and the surface velocity of the photoreceptor 1 are almost equal. During the series of control operations, the photoconductor 1 is, of course, rotating.

Therefore, by rotating the SR 34 while the SR 34 is in contact with the photoreceptor 1, the SR 34 in contact with the nip provided with the nip may disturb the image on the photoreceptor 1. There is no. Also, the image part α in the image area α
The carrier can be removed with almost no removal of the toner.

In these embodiments, the bias V1 applied to the SR 34 is applied to the image area α on the photosensitive member 1 where the toner corresponding to the electrostatic latent image is adhered.
1, the electric field in the direction of drawing the toner particles adhering to the background portion α2 and the surplus toner particles floating between the background portion α2 and the SR34 to the SR34 side. This is a bias voltage that generates an electric field that does not peel off the toner particles attached to the image portion α1 on the body 1.

Therefore, the bias V of the required voltage is applied to SR34.
By applying 1, the carrier in the image portion α1 can be removed with almost no removal of the toner, and the toner in the background portion α2 can also be removed.

Further, in these embodiments, a-Si (amorphous silicon) is used for the photoreceptor 1 as the image carrier, and damage due to contact with the DR 31 and SR 34, swelling and deterioration by the developer, etc. Can be reduced, and the life of the photoconductor 1 can be prolonged.

[0086]

As described above, according to the first aspect of the present invention, the operation in which the image area or the non-image area reaches or passes through the portion of the image carrier facing the sweep roller. The sweep roller and / or the developing roller are controlled to contact and separate from the image carrier and apply a bias voltage to the sweep roller and / or the developing roller in synchronization with the timing. By controlling the contact timing, it is possible to suppress wasteful consumption of the carrier, and to avoid occurrence of abnormal discharge with the image carrier.

According to the second aspect of the present invention, the sweep roller is brought into contact with the image carrier before the area on the image carrier on which the developer is applied reaches the portion facing the sweep roller. At the same time, a predetermined bias is applied to the sweep roller, and after the area where the developer is not applied reaches the portion facing the sweep roller, the sweep roller is separated from the image carrier and the bias is turned off. ing.

Therefore, the carrier liquid can be recovered with almost no removal of toner on the image because the sweep roller is in contact with the photosensitive member and the bias is applied before facing the developer layer. For this reason, the carrier liquid does not transfer to the next process (intermediate transfer body, transfer paper, etc.),
Since the recovery operation that becomes difficult when the carrier liquid enters the inside of the apparatus can be avoided, it is not necessary to complicate the apparatus and the process.

According to the eighth aspect of the present invention, after the preparatory area coated with the developer in the non-image area reaches the portion of the image carrier facing the sweep roller,
And, before the leading end of the image area arrives, while applying a predetermined bias to the sweep roller, after the rear end of the image area passes through the portion facing the sweep roller, and on the rear side The bias is configured to be turned off before the rear area of the non-image area where no developer is applied arrives.

Therefore, by applying a bias only to the portion where the developer layer is present on the image carrier, the latent image is prevented from being discharged, and the carrier liquid is recovered without almost removing the toner on the image. it can. As a result, it is possible to prevent the carrier liquid from being transferred to the next step (intermediate transfer member, transfer paper, or the like), so that it is possible to avoid extra devices and complicated processes.

According to the ninth aspect of the present invention, the sweep roller is moved to the image carrier before the preparatory area in the non-image area to which the developer is applied reaches the portion facing the sweep roller. Abuts on the sweep roller, in a portion facing the sweep roller, after the developer reaches the spare area after the developer in the non-image area is applied, and before the image area reaches the sweep roller. A predetermined bias is applied between the sweep roller and the image carrier.

Therefore, the sweep roller is brought into contact with the developer layer on the image carrier just before the portion where the developer layer is present, and a bias is applied to the portion where the developer layer is present, so that the sweep roller can be permanently deformed or abnormal due to the sweep roller. Discharge can be prevented.

According to the tenth aspect of the present invention, a predetermined bias is applied to the portion facing the sweep roller after the preliminary area before the developer in the non-image area reaches the preliminary area. The sweep roller described above is brought into contact with the image carrier.

Accordingly, by contacting the biased SR with the image carrier at the portion where the developer layer on the image carrier is present, the sweep roller comes into contact with the toner and almost all of the toner on the image is removed. In addition, the carrier liquid on the image carrier can be collected and removed. As a result, it is possible to prevent the carrier liquid from being transferred to the next step (such as an intermediate transfer member or transfer paper).

According to the eleventh aspect of the present invention, the sweep roller is used to carry the image after the preliminary area where the developer in the non-image area is applied reaches the portion facing the sweep roller. Abuts on the body, and then applies a predetermined bias to the sweep roller, and after the rear end of the image area reaches a portion facing the sweep roller, and the developer in the non-image area. It is characterized in that the bias is turned off and the sweep roller is separated from the image carrier before the rear area where the coating is not performed arrives.

Therefore, the sweep roller is brought into contact with the image carrier at a portion where the developer layer on the image carrier is present, and then a bias is applied to the sweep roller. Abnormal discharge does not occur when contacting Further, the carrier liquid on the image carrier can be removed, and transfer of the carrier liquid to the next step (intermediate transfer member, transfer paper, or the like) can be prevented. In particular, the carrier liquid can be recovered with little removal of the toner on the image.

In the portion where the developer layer on the photoreceptor is located,
By turning off the bias applied to the sweep roller and separating the sweep roller from the image carrier, abnormal discharge by the sweep roller and permanent deformation of the sweep roller can be prevented when the carrier liquid on the image carrier is removed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a copying machine including a developing device to which an image forming method of the invention is applied.

FIG. 2 is an explanatory diagram showing an image area and the like on a photoconductor.

FIGS. 3A and 3B are explanatory diagrams showing a contact state between a photoconductor and a developing roller, wherein FIG. 3A shows an image portion and FIG. 3B shows a background portion.

4A and 4B are explanatory diagrams showing a contact state between a photoconductor and a sweep roller, wherein FIG. 4A shows an image portion and FIG. 4B shows a background portion.

FIGS. 5A and 5B show a first embodiment of the present invention, in which FIG. 5A is an explanatory diagram showing a formation position of an image area or the like of a photoconductor, and FIGS. 5B, 5C, and 5D are sweep rollers. 4 is a time chart showing a bias application operation, a sweep roller contact operation, and a sweep roller rotation operation, respectively.

FIGS. 6A and 6B show a modified example of the first embodiment of the present invention, wherein FIG. 6A is an explanatory diagram showing a formation position of an image area or the like of a photoconductor, and FIGS. Contact operation,
It is a time chart which shows the contact operation of a sweep roller, respectively.

FIGS. 7A and 7B show a second embodiment of the present invention, wherein FIG. 7A is an explanatory diagram showing a formation position of an image area or the like of a photoconductor, and FIGS. 7B and 7C are contact operations of a sweep roller. 5 is a time chart illustrating a bias application operation of a sweep roller.

FIGS. 8A and 8B show a modified example of the second embodiment of the present invention, wherein FIG. 8A is an explanatory view showing a formation position of an image area or the like of a photoconductor, and FIGS. 5 is a time chart illustrating a contact operation and a sweep roller bias application operation, respectively.

FIGS. 9A and 9B show still another modified example of the second embodiment of the present invention, in which FIG. 9A is an explanatory view showing a formation position of an image area or the like of a photoconductor, and FIGS. 6 is a time chart illustrating a contact operation of the sweep roller and a bias application operation of the sweep roller.

FIGS. 10A and 10B show a third embodiment of the present invention, wherein FIG. 10A is an explanatory diagram showing a position where an image area of a photosensitive member is formed, and FIG. 10B is a time chart showing a bias applying operation of a sweep roller. It is.

FIGS. 11A and 11B show a modified example of the fourth embodiment of the present invention, wherein FIG. 11A is an explanatory view showing a formation position of an image area or the like of a photoconductor, and FIGS. 5 is a time chart illustrating a contact operation and a sweep roller bias application operation, respectively.

FIGS. 12A and 12B show a modified example of the fifth embodiment of the present invention, in which FIG. 12A is an explanatory view showing a formation position of an image area or the like of a photoconductor, and FIGS. 5 is a time chart illustrating a contact operation and a sweep roller bias application operation, respectively.

FIGS. 13A and 13B show a modified example of the sixth embodiment of the present invention, wherein FIG. 13A is an explanatory view showing a formation position of an image area or the like of a photoconductor, and FIGS. 5 is a time chart illustrating a contact operation and a sweep roller bias application operation, respectively.

FIGS. 14A and 14B show a modified example of the seventh embodiment of the present invention, wherein FIG. 14A is an explanatory diagram showing a formation position of an image area or the like of a photoconductor, and FIGS. 5 is a time chart illustrating a contact operation and a sweep roller bias application operation, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (image carrier) 2 Exposure device 3 Developing device 31 Developing roller (DR) 34 Sweep roller (SR) 4 Transfer device 5 Static electricity removal value 6 Cleaning device 7 Charging device α Image area α1 Image area α2 Background area β ( Non-image area on the front side β1 front area β2 pre-spare area γ (rear) non-image area γ1 back area γ2 post-spare area

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsutomu Sasaki 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H073 BA09 BA13 BA21 CA32 2H074 AA03 BB42 CC28 CC33

Claims (12)

[Claims] A developing roller that can be brought into contact with and separated from an image carrier that develops an image area on the image carrier where an electrostatic latent image is formed;
A sweep roller capable of coming into contact with and separating from an image carrier for collecting and removing the carrier liquid after development and unnecessary toner adsorbed in the non-image area, wherein the sweep roller on the image carrier is provided. The operation of approaching / separating the sweep roller and / or the developing roller from / to the image carrier and the operation of applying a bias voltage to the sweep roller and / or the developing roller in synchronization with the operation in which the image area or the non-image area reaches or passes the opposing portion. And an image forming method. 2. A method according to claim 1, wherein the sweep roller is connected to the image carrier before the preparatory area in the front non-image area on the image carrier to which the developer has been applied reaches a portion facing the sweep roller. A predetermined bias is applied to the sweep roller while being brought into contact with the sweep roller.After the rear area where the developer in the non-image area on the rear side is not applied arrives at a portion facing the sweep roller, the sweep roller is moved. 2. The image forming method according to claim 1, wherein the bias is turned off while separating from the image carrier. 3. The method according to claim 1, wherein the sweep roller is brought into contact with the image carrier before the bias is applied, and the sweep roller is separated from the image carrier after the bias is turned off. 3. The image forming method according to item 2. 4. Only when a developer is applied on the developing roller, the developing roller comes into contact with the image carrier, and before a predetermined time elapses from when the developing roller comes into contact with the image carrier, 3. The image forming method according to claim 2, wherein the sweep roller starts to contact the image carrier. 5. The sweep roller is brought into contact with an image carrier and a predetermined bias is applied to the sweep roller before the image area reaches a portion facing the sweep roller. 2. The image forming method according to claim 1, wherein after the end passes through a portion facing the sweep roller, the sweep roller is separated from the image carrier and the bias is turned off. 6. When the sweep roller is brought into contact with the image carrier and a developer is applied on the image carrier when the bias is applied, the sweep roller is brought into contact with the image carrier. 6. The image forming method according to claim 5, wherein the bias is applied prior to the contact. 7. An image forming apparatus according to claim 6, wherein the image bearing member is provided with a sweep roller and a sweep roller. 6. The image forming method according to claim 5, wherein a bias applied to the sweep roller is cut off after the sweep roller is separated from the image carrier, and after the sweep roller is separated from the image carrier. . 8. The image forming apparatus according to claim 1, wherein said front non-image area has a front preliminary area coated with a developer and reaches a portion facing said sweep roller on said image carrier. A predetermined bias is applied to the sweep roller before reaching, and when the rear end of the image area passes through a portion facing the sweep roller, and after the developer in the non-image area on the rear side 2. The image forming method according to claim 1, wherein the bias is turned off before the rear area where no ink is applied arrives. 9. A sweep roller is brought into contact with an image carrier before a preparatory area in a front non-image area on which developer is applied reaches a portion facing the sweep roller. The opposite portion, after the developer in the rear non-image area is applied after the preliminary area arrives, and before the image area, before the sweep roller and the image carrier. 2. The image forming method according to claim 1, wherein a predetermined bias is applied to the sweep roller during the period. 10. The sweep roller, to which a predetermined bias has been applied, is applied to the image forming apparatus after the preliminary area in the front non-image area where the developer is applied arrives at a portion facing the sweep roller. 2. The image forming method according to claim 1, wherein the image forming apparatus contacts the carrier. 11. A sweep roller is brought into contact with an image carrier after a preliminary area before application of a developer in the non-image area on the front side reaches a portion facing the sweep roller, and thereafter, Applying a predetermined bias to the sweep roller, after the rear end of the image area reaches the portion facing the sweep roller, and after the developer is not applied in the rear non-image area. 2. The image forming method according to claim 1, wherein the bias is turned off before the area reaches, and the sweep roller is separated from the image carrier. 12. When the developer is applied on the developing roller, the developing roller is brought into contact with the image carrier, and the developing roller is brought into contact with the image carrier X
After a lapse of seconds (where X = L / v, L: distance between the developing roller and the sweep roller on the image carrier, v: linear velocity of the image carrier), the bias is applied to the sweep roller, and The developing roller is separated from the image carrier when the developer is applied on the developing roller, and the X is determined when the developing roller is separated from the image carrier.
2. The image forming method according to claim 1, wherein the bias is turned off before a lapse of seconds.